Trying to understand apple stock movements.

I am perplexed at to why the stock is again on a huge (all time?) high, and shows the same upward trend as about the same time last year. Yet in the past three years we've seen it go through a very high crest around mid year or a bit later as in the case of 2007, and then a slow slump, and then a crest and a slump again. And with fluctuations as high as that of almost doubling the price and then returning to the 100s

I have very little to none experience in the stock markets. Is this a natural thing, or rather let me rephrase that, is this an explanation for this rationally available? Do big funds buy ins and outs influence aapl or is it more stable to these and more attuned to the actual goings on in the co.

Excuse my ignorance if all these sound bland and formulaic, if not downright completely wrong.